In patients non-proliferative disseminated tumour cells (DTCs) can persist in the bone marrow (BM) while other organs (i.e. lung) present growing metastasis. This suggested that the BM might be a metastasis “restrictive soil” by encoding dormancy-inducing cues in DTCs. Here we show in a HNSCC model that strong and specific TGFβ2 signalling in the BM activates p38α/β, inducing a [ERK/p38]low signalling ratio. This results in induction of DEC2/SHARP1 and p27, downregulation of CDK4 and dormancy of malignant DTCs. TGFβ2-induced dormancy required TGFβ-receptor-I, TGFβ-receptor-III and SMAD1/5 activation to induce p27. In lungs, a metastasis “permissive soil” with low TGFβ2 levels, DTC dormancy was short lived and followed by metastatic growth. Importantly, systemic inhibition of TGFβ-receptor-I or p38α/β activities awakened dormant DTCs fueling multi-organ metastasis. Our work reveals a “seed and soil” mechanism where TGFβ2 and TGFβRIII signalling through p38α/β regulates DTC dormancy and defines restrictive (BM) and -permissive (lung) microenvironments for HNSCC metastasis.

Tumor invasion, angiogenesis and metastasis involve secretion of proteolytic enzymes and cell migration into blood vessels. Tumor cells are capable of degrading the extracellular matrix via a proteolytic cascade that includes urokinase-type plasminogen activator (uPA) and matrix metalloproteases (MMPs). We have investigated the antitumor and antiangiogenic properties of soy isoflavone genistein in B16 melanoma and F3II mammary carcinoma mouse models. At non-cytotoxic concentrations (0.1-50 μM) genistein induced dosedependent spindle-cell morphology and significantly reduced motility in both cell lines. Genistein inhibited uPA secreted by F3II cell monolayers, while inducing an increase in the proteolytic activity of B16 cells. On the contrary, the compound did not modify the MMP-9 and-2 produced by tumor cells. In vivo, i.p. administration of genistein at a dose of 10 mg/kg/ day reduced tumor-induced angiogenesis in syngeneic mice implanted with B16 or F3II cells. Similar antiangiogenic effects were obtained with a soybean-based diet. This data suggest that tumor cell migration and proteolysis may be associated with the antitumor and antiangiogenic activity of soy isoflavone genistein.

Telomerase is the enzyme responsible for maintenance of the length of telomeres by addition of guanine-rich repetitive sequences. Telomerase activity is exhibited in gametes and stem and tumor cells. In human somatic cells, proliferation potential is strictly limited and senescence follows approximately 50–70 cell divisions. In most tumor cells, on the contrary, replication potential is unlimited. The key role in this process of the system of the telomere length maintenance with involvement of telomerase is still poorly studied. Undoubtedly, DNA polymerase is not capable of completely copying DNA at the very ends of chromosomes; therefore, approximately 50 nucleotides are lost during each cell cycle, which results in gradual telomere length shortening. Critically short telomeres cause senescence, following crisis and cell death. However, in tumor cells the system of telomere length maintenance is activated. Much work has been done regarding the complex telomere/telomerase as a unique target, highly specific in cancer cells. Telomeres have additional proteins that regulate the binding of telomerase. Telomerase, also associates with a number of proteins forming the sheltering complex having a central role in telomerase activity. This review focuses on the structure and function of the telomere/telomerase complex and its altered behavior leading to disease, mainly cancer. Although telomerase therapeutics are not approved yet for clinical use, we can assume that based on the promising in vitro and in vivo results and successful clinical trials, it can be predicted that telomerase therapeutics will be utilized soon in the combat against malignancies and degenerative diseases. The active search for modulators is justified, because the telomere/telomerase system is an extremely promising target offering possibilities to decrease or increase the viability of the cell for therapeutic purposes.

Protein Kinase CK2 is a serine-threonine kinase frequently deregulated in many human tumors. Here, we hypothesized that a peptide binder to the CK2 phosphoacceptor site could exhibit anticancer properties in vitro, in tumor animal models, and in cancer patients. By screening a random cyclic peptide phage display library, we identified the CIGB-300 (formerly P15-Tat), a cyclic peptide which abrogates the CK2 phosphorylation by blocking recombinant substrates in vitro. Interestingly, synthetic CIGB-300 led to a dose-dependent antiproliferative effect in a variety of tumor cell lines and induced apoptosis as evidenced by rapid caspase activation. Importantly, CIGB-300 elicited significant antitumor effect both by local and systemic administration in murine syngenic tumors and human tumors xenografted in nude mice. Finally, we performed a First-in-Man trial with CIGB 300 in patients with cervical malignancies. The peptide was found to be safe and well tolerated in the dose range studied. Likewise, signs of clinical benefit were clearly identified after the CIGB-300 treatment as evidenced by significant decrease of the tumor lesion area and histological examination. Our results provide an early proof-of-principle of clinical benefit by using an anti-CK2 approach in cancer. Furthermore, this is the first clinical trial where an investigational drug has been used to target the CK2 phosphorylation domain.

CIGB-300, formerly known as P15-tat, is a proapoptotic peptide with established antiproliferative activity in vitro and antitumoral activity in vivo. This hypothesis-driven peptide was initially selected for its ability to impair the in vitro CK2-mediated phosphorylation in one of its substrates through direct binding to the conserved acidic phosphoaceptor domain. However, the actual in vivo target(s) on human cancer cells among the hundreds of CK2 substrates as well as the subsequent events that lead to apoptosis on tumor cells remains to be determined. In this work, we identified the multifunctional oncoprotein nucleophosmin/B23 as a major target for CIGB-300. In vivo, the CIGB-300-B23 interaction was shown by pull-down experiments and confirmed by the early in situ colocalization of both molecules in the cell nucleolus. Moreover, CIGB-300 inhibits the CK2-mediated phosphorylation of B23 in a dose-dependent fashion both in vitro and in vivo as shown using the recombinant GST fusion protein and the metabolic labeling approach, respectively. Such phosphorylation impairment was correlated with the ability of CIGB-300 to induce nucleolar disassembly as documented by the use of established markers for nucleolar structure. Finally, we showed that such a sequence of events leads to the rapid and massive onset of apoptosis both at the molecular and cellular levels. Collectively, these findings provide important clues by which the CIGB-300 peptide exerts its proapoptotic effect on tumor cells and highlights the suitability of the B23/CK2 pathway for cancer-targeted therapy.

Lovastatin, a fungal antibiotic used in the treatment of hypercholesterolemia, is an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, the key regulatory enzyme in the mevalonate pathway of cholesterol synthesis. We examined the antitumor properties of lovastatin on the F3II sarcomatoid mammary carcinoma, a highly invasive and metastatic murine tumor model. Female BALB/c inbred mice were inoculated subcutaneously with F3II tumor cells and injected i.p. daily with 10 mg/kg body weight of lovastatin or administered p.o. at a level corresponding to the human dosage of 1-2 mg/kg/day. Treatment significantly prolonged tumor latency and reduced tumor formation and metastatic dissemination to the lungs from established mammary tumors. In vitro, antitumor properties of lovastatin were strongly associated with inhibition of tumor cell attachment and migration. These actions were prevented by addition of mevalonate but not by equivalent concentrations of farnesyl pyrophosphate. In accordance, Western blot assays showed that lovastatin effects did not appear to be related to modifications in Ras oncoproteins in our model. The present data indicate that lovastatin could be an antitumor agent with potentially useful clinical applications in breast cancer.

No abstract

The antitumor efficacy of the CK2 inhibitors so far described has not been extensively evaluated in cancer animal models. We have previously demonstrated that a proapoptotic cyclic peptide termed P15 delivered into the cells by the Tat Cell Penetrating Peptide was able to abrogate the CK2-mediated phosphorylation and induce tumor regression when injected directly into solid tumors in mice. Here we explored the antitumor effect by systemic administration of P15-Tat in a consecutive 5-day schedule through either intraperitoneal or intravenous route. Importantly, significant delay of tumor growth was observed at 2 mg/kg (p < 0.05), 10 mg/kg (p < 0.01) or 40 mg/kg (p < 0.001) after P15-Tat administration both in syngeneic murine tumors and human tumors xenografted in nude mice. In line with this, the systemic administration of P15-Tat induced apoptosis in the tumor as evidenced by in situ DNA fragmentation. Furthermore, we evidenced that 99m Tc-labeled P15-Tat peptide was certainly accumulated on the tumors after administration by both routes. This report becomes the first describing the antitumor effect induced by systemic administration of a peptide that targets the acidic phosphorylation domain for CK2 substrates. Also, our data reinforces the perspectives of P15-Tat for the cancer targeted therapy. ' 2007 Wiley-Liss, Inc.